Double-acting reciprocating pump



June 7, 1949. M. COVlNS 2,472,647

DOUBLE-ACTING RECIPRQCATING PUMP Filed May 9, 1945 MEYER Cor/Mr fiii orneys Patented June 7, 1949 UNITED STATES ATENT OFFICE 1 Claim.

This invention relates to a pump and more particularly to a pump for pumping or compressing gases in an efficient and economical manner. While the pump of this invention is particularly adapted for pumping gases because of its high emciency it may also be used to pump liquids. A pump eflicient for pumping liquids is not necessarily efficient for pumping gases but an efi'icient gas pump is necessarily efficient for pumping liquids.

It is an object of this invention to provide an improved reciprocating type pump actuated by a crank.

It is a further object of the invention to provide a novel arrangement in construction whereby an interconnected double headed and double acting piston is actuated by a crank and the lubrication accomplished by a splash system.

It is another object of the invention where it is important in pumping gases to prevent excess lubricating oil being discharged with the gas, to provide a novel arrangement of oil rings and interconnection between the piston heads. In some cases it is desirable to use a felt oil soaked pad attached to the piston which lubricates the piston in the form of a spray rather than by the splash method.

Still another object of the invention is to provide an improved arrangement of the inlet and outlet valves which results in a more eflicient pump and which is necessary for pumping gases which are more difiicult to pump efficiently than liquids.

It is also an object of the invention to provide a small compact pump of large capacity which is economical to build and to operate.

A further object of the invention is to provide an arrangement of the actuating crank so as to take as little space as possible leaving more room for the pistons thereby increasing the efficiency several hundred percent over previous gas pumps.

It is also an object of the invention to provide a rotatable contact associated with the mechanical means actuating the piston which greatly reduces the friction and makes the pump more efiicient.

Generally the invention involves a compact cylinder having a doubleheaded interconnected piston arranged to reciprocate in the cylinder, said piston having a slot in the center thereof with its longitudinal dimension at right angles to both the direction of reciprocation of the piston and to the axis of a crank operatively associated in said slot for reciprocating the piston when the crank is turned. The particular driving means for turning the crank is not important to this invention since a motor, engine or any other suitable prime mover may be used.

The same problems are not involved in providing for an efficient gas pump as in a liquid pump. The problem are more difiicult and not as easily solved. It is more difficult to have sufficient tolerance between the piston and the walls of the cylinder and yet prevent leakage. It is more difficult to lubricate and care must be taken to provide proper inlet and outlet valves for eificient operation which is not so critical for a liquid pump.

The pump in the present invention has many uses. One of its most important uses is as a tractor pump wherein the crank in the pump is attached to the power take off of the tractor motor and used as an air compressor. It can also be attached to trucks and automobiles as a tire pump. It may also be used as an air compressor pump in filling stations and the like. The pump is compact and eflicient so that it can be used as a portable pump Wherever a gas compressor is desired.

My pump may also be used as the source of compressed air in spray guns for spraying insects, fruit trees, paint and the like.

One big advantage of my pump is that low friction loss permits the pump to be driven by a pulley and belt whereas in previous pumps of this kind because of high friction losses a positive drive like a chain was required.

Another advantage of this pump is in the novel arrangement of the piston and crank permitting the use of a straight pipe or casting which makes the pump simple and economical to construct.

Other advantages, objects and uses of the pump will become apparent by referring to the drawings in which Figure 1 is a cross sectional perspective view of the pump assembly; Figure 2 is a perspective drawing of one type of double headed interconnected piston which may be used; Figure 3 is another type of double headed innerconnected piston particularly suitable where it is important to insure that no excess lubricating oil is discharged along with the compressed gases. Figure 4 is a perspective view of the half crank.

Referring to Figures 1 and 2 cylinder iii having heads ll threaded thereon is provided for containing the piston l4. This pump is primarily designed to lie in a horizontal position While being used and it may be in the horizontal position as shown in Figure 1.

In heads H of the cylinder it are provided inlet valves l2 shown as tappets although other suitable types may be used. Also in the heads II are discharge valves [3 which are of the ballcheck type although any other suitable conventional type may be used within the scope of the invention. Although not shown the two discharge valves l3 may be connected to a common heater so as to have a uniform flow of the gas compressed by the double acting piston.

Piston M havin heads l5 and I5 interconnected by the connecting element l1 provides the moving element in the pump for the compression of the gases. Heads l5 and are provided with a number of grooves in which are placed suitable piston rings and oil rings such as piston rings [8 and oil rings is. Also slots '20 may be provided with a piston ring or compression ring although such a ring is left out of the drawing in order to show the construction of the grooves in the piston heads. A slot 2| in the center of the piston in the connectin element i7 is provided with oil openings 22. The slot does not extend entirely through the piston or the connecting element ll although it is within the scope of the invention to do so and in that case the extended opening takes the place of openings 22. The bearing slot 2| is at right angles to the direction of reciprocation of the piston and also at right angles to the of crank 2d. Slots 22 permit lubricating oil to enter the slot 2! for lubricating the rotatable bearing associated with the slot.

The oil rings L! that are somewhat similar to compression or piston rings is with exception that they have openings therein for permitting lubricating oil to return to the bulk source rather than being forced out through the discharge valves. Openings, 23 are, provided in the piston heads to connect with openings in the oil rings, to drain excess oil back into the bulk supply. Openings 23 are right angle openings as indicated to drain the excess oil back into the bulk supply of oil contained between the inner faces of the piston heads, thereby preventin excess seepage toward the discharge valves. Oil is introduced into the cylinder through a screw plug at the top which is not shown since this is a well known method for lubricating cylinders. The reciprocating motion of the pump splashes the oil in such a manner that the piston is properly lubricated and also splashes the oil through the opening 22 into slot 2| so as to lubricate the rotatable bearing. herein. This is known as the splash system of lubrication.

Half crank 24 is provided made up of sections 25 and 26. he half crank is preferably made in two sections for ease in assembling and although it could be made in one piece, it would be more difiicult to construct and more complicated to assemble. Also it is within the scope of the invention to make the crank in three sections or parts. The two sections 25 and 26; arejoined by a threaded connection as shown. The section 25 has a larger section or shoulder thereby forming a bear-. ing surface on the annular boss 21 extending on the outside of the cylinder. The semi-spherical portion 28 of section 26 also is enlarged to provide a bearing surface on the interior of the cylinder as indicated at 29. The remaining part 30 of section 26 is the portion of the crank operatively associated in the slot 2! which causes the cylinder to reciprocate when the crank is turned. A sleeve bearing 3| is placed around this section of the crank 39 so as to 'freely rotate in the slot 2| providing a rotary driving action when the crank is turned greatly reducing the friction over any other bearings previously used in pumps of this type. Although not shown in the drawing, end

4 32 of the crank may be attached to any mechanical means such as a power take off of a tractor or motor for turning the crank which causes the piston to reciprocate. It may be driven by a belt connected to a pulley end 32.

Figure 3 illustrates another shape of piston and is similar to the piston illustrated in Figure 2. It is adapted to insure that the excess lubricating oil from the splash system does not work its way past the oil in the piston rings so as to be discharged through the valves along with the compressed gas. Furthermore it provides an easier means for drilling the openings 34. Openings 23 in the piston of Figure 2 are right angle openings which involve two operations in the drilling of the holes whereas the holes 34 in the piston shown in Figure 3 extend directly through the piston to the oil rings and may be made in one drilling operation. The connecting element l! which connects the two heads 15 and It of the piston in Figure 3 is cut away and fixedly attached to a recess in the cylinder heads as shown. The solid bearing surface extending between the heads of the piston in Figure 2 is thereby eliminated by the construction shown in Figure 3 which prevents the excess oil from being driven in the direction toward the exhaust valves as is the. tendency in the construction shown in Figure 2 Another means {or lubrication. which has certain advantages, is the provision of a pad made of felt or other material having absorbing properties which is attached on the side of the connecting element l'l opposite the openings in the back wall of the slot 2i. Through the oil plu in cylinder l0, lubricant is poured on the felt pad and the reciprocating movement of, the piston causes the oil to form in a fine spray or mist thereby lubricating the piston. The fine mist also. enters through the openings 22 to, lubricate that hearing area. The fine mist or spray in this system minimizes the tendency Of the. oil to work its way towards the exhaust valves as is the case in other systems, of lubrication.

It also within the scope of this. invention to use a roller bearing in place of the sleeve. hearing 2|. A roller bearing may also be used within the boss 2! to reduce the friction of the crank turnin in the boss.

It is also within. the. scope or my invention to lubricate the pump in the following manner. Instead of havin the. oil reservoir contained between the. inner faces, of the two. piston heads, the piston can be a straight cylinder hollowed out in the center and the oil supply contained, in the hollowed ou v portion. The oil, lubricates. the exterior surface of, the piston and the interior surface of the cylinder through holes bored through the piston Wall to the. oil supply. The movement, of. the piston. will splash sufiicient oil through the holes. to. obtain, the desired lubrication. By this system the amount oi lubrication can be, controlled by the size, spacing andnumher or the holes. Furthermore, lubrication can be obtained at the desired and proper points. by the suitable positioning of the oil holes. It. may be desirable to lubricate certain portions of the pump. more than, other portions and this, also. can be controlled by the. size, number and position of th oil holes. One. of the. advantages of this type oi lubrication over the usual type. oi splash system. i that there is no oil pool, in the bottom of the cylinder which tends to work past. the piston and oil rings toward the exhaustvalves.

Furthermore, in. the. usual. splashsystem; it. is.

not possible to, control the, amount of oil cover- 5 ing the bearing surfaces as is the case in this method of lubrication. While this method of lubrication is particularly adaptable for horizontal pumps and motors, it also is advantageous for use in lubricating any type of moving part like a piston.

The above description of the drawings is given as an example and is not intended to limit the invention which is only limited by the following claim.

I claim as my invention:

In a pump, a tube of uniform internal diameter throughout its length forming a cylinder, a piston therein having two' longitudinally spaced heads connected by a longitudinally extending web having a thickness substantially less than 15 the internal diameter of said cylinder, a slot in said web extending at a right angle to the longitudinal axis of the piston, a hollow boss extendin outwardly from the wall of said cylinder forming a bearing, a shaft journaled in said bearing and extending into the interior of said cylinder, a crank arm removably secured to the inner end of said shaft and positioned between said web and the inner wall of said cylinder, the surface of said crank arm adjacent the inner wall of said cylinder being of curved configura- REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 206,655 Wolf July 30, 1878 586,669 Shedlock July 20, 1897 612,226 Bailey Oct. 11, 1898 975,233 Hanna Nov. 8, 1910 20 1,368,598 Anderson Feb. 15, 1921 1,449,537 Neighbour et a1 Mar. '7, 1923 1,890,238 Smith et a1. Dec. 6, 1932 FOREIGN PATENTS 25 Number Country Date 551,295 France 1923 

